1. Field of the Invention
The present invention relates to optical systems that utilize an attenuator to selectively attenuate an optical signal sent from a signal source to a detector over an optical fiber. More particularly, the present invention relates to the structure of the attenuator and the optical detector as well as the control systems for both the attenuator and the optical detector.
2. Description of the Prior Art
In optical data communications, signals are typically transmitted from a signal source to a signal receiver over an optical fiber network. Optical signal receivers have a signal intensity range in which they function best. If a signal falls below the operational range, the optical signal receiver may fail to detect the signal. Alternatively, if the intensity of a signal exceeds the operational range of the optical signal receiver, the receiver may become saturated and register nonlinear effects.
In the field of optical data communications, optical signals are typically received either by a digital optical receiver or an analog optical receiver. In general, digital optical receivers have a greater signal intensity range than do analog optical receivers. For example, the Model 1319 high-speed digital receiver manufactured by Lucent Technologies, Inc. of Murry Hill, N.J. has a dynamic operational range of approximately 25 dB. However, analog optical receivers have a typical dynamic operational range of between 3 dB and 5 dB. For these reasons, in optical data communications systems, especially those that use analog optical receivers, the optical receiver, must be matched to the signal strength at the point of signal reception. If the signal source changes, or the optical fiber network is altered, the optical receivers must be adjusted or replaced to match any change in the received signal intensity.
A need therefore exists in the art for a system that automatically attenuates a signal received by an optical receiver so that the signal read by the optical receiver falls within its operational range. Such a system would eliminate the need to adjust or replace the optical detectors in a system should the signal intensity in an optical fiber system change for any reason.